Surface topography detector and method for use of the same

ABSTRACT

A surface topography detector includes a first sensor, a second sensor and a digital control unit. The angle defined between the center axis of the first sensor and the center axis of the second sensor is equal to or less than 90 degrees. The digital control unit is electrically connected with the first sensor and the second sensor and is arranged for controlling the movement of the first sensor and the second sensor and processing the output signals of the first sensor and the second sensor. The surface topography detector can detect a surface with a bigger range of gradient angle accurately.

FIELD OF THE INVENTION

The present invention relates to surface topography detectingtechnologies and, more particularly, to a surface topography detectorand a method for detecting surface topography of a workpiece.

DESCRIPTION OF RELATED ART

In recent years, mobile phones with cameras have been rapidly gaining inpopularity. An aspherical lens used in mobile phone cameras can be asthin as about 1 mm whilst requiring a surface precision of about ±1 μm.

It is well known that lenses can be produced by injection molding, butone difficulty has always been apparent. In order to produce lenses withthe desired level of precision, the molds used in the injection moldingrequire an equally high level of precision.

Referring to FIG. 2, in a related surface topography machining processfor an aspherical workpiece, a surface topography detector is usuallyused to detect surface topography of the aspherical workpiece. Aconventional surface topography detector includes a sensor 2 and adigital control unit 3. The sensor 2 is used for detecting the surfaceof the workpiece. The digital control unit 3 is used for processingoutput signals from the sensor 2 and controlling movement of the sensor2. When the conventional surface topography detector detects a surface1, in order to get accurate information on the surface 1, an angle βformed between a center axis of the sensor 2 and a tangential plane ofthe surface 1 should be bigger than 45 degrees. The gradient angle ofthe axis of sensor 2 usually cannot change during surface topographydetecting process. So, the surface topography detector with only onesensor 2 cannot accurately detect the surface 1 with a gradient angle θbigger than 45 degrees.

What is needed, therefore, is a surface topography detector which canaccurately detect a surface within a larger gradient angle range.

SUMMARY OF THE INVENTION

In accordance with one embodiment, a surface topography detectorincludes a first sensor with a first central axis, a second sensor witha second central axis and a digital control unit. The angle definedbetween the first center axis and the second center axis is equal to orless than 90 degrees. The digital control unit is electrically connectedwith the first sensor and the second sensor and is configured forprocessing output signals from the first sensor and the second sensorand controlling movement of the first sensor and the second sensor.

In accordance with an embodiment, a method for detecting a surfacetopography of a workpiece includes the steps of: arranging a firstsensor with a first central axis and a second sensor with a secondcentral axis in a manner such that an angle is defined between the firstcenter axis and the second center axis, the angle being equal to or lessthan 90 degrees; determining detecting locations of the first sensor andthe second sensor; detecting the locations on the surface using thefirst sensor and the second sensor; and processing output signals fromthe first sensor and the second sensor thereby obtaining a result.

Other advantages and novel features of the present surface topographydetector and method for detecting a surface topography of a workpiecewill become more apparent from the following detailed description whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present surface topography detector and method fordetecting a surface topography of a workpiece can be better understoodwith reference to the following drawings. The components in the drawingsare not necessarily drawn to scale, the emphasis instead being placedupon clearly illustrating the principles of the present surfacetopography detector and method for detecting a surface topography of aworkpiece. Moreover, in the drawings, like reference numerals designatecorresponding parts throughout the several views.

FIG. 1 is a schematic, plan view of a surface topography detectoraccording to a preferred embodiment of the present invention; and

FIG. 2 is a schematic, plan view of a conventional surface topographydetector.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present surface topography detector and method fordetecting a surface topography of a workpiece will now be described indetail below and with reference to the drawings.

Referring to FIG. 1, a surface topography detector 100 according to apreferred embodiment includes a first sensor 201 with a first centralaxis, a second sensor 202 with a second central axis and a digitalcontrol unit 30. An angle α defined between the first center axis andthe second center axis can be equal to or less than 90 degrees. Thedigital control unit 30 is electrically connected with the first sensor201 and the second sensor 202. The digital control unit 30 is configuredfor processing output signals from the first sensor 201 and the secondsensor 202 and controlling movement of the first sensor 201 and thesecond sensor 202.

The first sensor 201 and second sensor 202 can be optical interferencesensors or inductive transducers. Preferably, the angle α definedbetween the first central axis of the first sensor 201 and the secondcenter axis of the second sensor 202 is less than 90 degrees.

The digital control unit 30 can control the movement of the first sensor201 and the second sensor 202. The digital control unit 30 can alsoprocess the output signals of the first sensor 201 and the second sensor202, and obtain a detecting result. The output signals of the firstsensor 201 and the second sensor 202 include information of surfacetopography of a detected location on the workpiece 10 and correspondingpositions of the first sensor 201 and the second sensor 202.

Referring to FIG. 1, in operation of the surface topography detector100, the first sensor 201 can detect a first surface 101 and the secondsensor 202 can detect a second surface 102. The first surface 101 is apart of the surface of workpiece 10 at the right of a center axis of thesurface of workpiece 10. The second surface 102 is a part of surface ofworkpiece 10 at the left of the center axis of the surface of workpiece10. In order to get an accurate information of the first surface 101,the angle β defined between an center axis of the first sensor 201 andthe tangential plane of the first surface 101 should be equal to orbigger than 45 degrees. Thus the first sensor 201 can accurately detectthe first surface 101 with a gradient angle θ equal to or less than 45degrees. Accordingly, the surface topography detector 100 with the firstsensor 201 and the second sensor 202 can detect the workpiece 10 with asurface with a gradient angle θ equal to or less than 90 degrees.

Furthermore, the present invention also provides a method for detectingsurface topography of a workpiece 10, according to an embodiment, themethod includes the following steps.

First step: arranging a first sensor 201 with a first central axis and asecond sensor 202 with a second central axis in a manner such that anangle α is defined between the first center axis and the second centeraxis, the angle being equal to or less than 90 degrees. The surface ofthe workpiece 10 has a gradient angle θ equal to or less than 90degrees. The first sensor 201 and the second sensor 202 can be opticalinterference sensors or inductive transducers. The angle α can be setbases the gradient angle θ of the surface of the workpiece 10 insuringthe angle defined between the first sensor 201 and the tangential planeof the first surface 101 and the angle defined between the second sensor202 and the tangential plane of the second surface 102 are equal to orbigger than 45 degrees. The first sensor 201 takes charge of detectingthe first surface 101 and the second sensor 202 takes charge ofdetecting the second surface 102. The detecting routes of the firstsensor 201 and the second sensor 202 can be set by the program in adigital control unit 30. The angle α is unchangeable during surfacetopography detecting process.

Step 2: determining detecting locations of the first sensor 201 and thesecond sensor 202. In present embodiment, the first sensor 201 detectsthe first surface 101 and the second sensor 202 detects the secondsurface 102.

Step 3: detecting the locations on the surface using the first sensorand the second sensor.

Step 4: processing output signals from the first sensor 201 and thesecond sensor 202 thereby obtaining a detecting result. In the step 4, adigital control unit 30 is used for processing the output signals of thefirst sensor 201 and the second sensor 202 and obtaining a detectingresult. The result of the detecting process can be gained by comparingthe information on the surface of the workpiece 10 with information on astandard workpiece.

As stated above, the present surface topography detector and the methodfor detecting a surface topography of a workpiece use two sensorsorientated at an angle α to detect a surface of a workpiece. Becauseeach sensor can detect a surface with a gradient angle θ equal to orbigger than 45 degrees, the surface topography detector and the methodfor detecting a surface topography of a workpiece can detect a surfacewith a gradient angle θ equal to or less than 90 degrees. Accordingly,the present surface topography detector can detect a surface with abigger range of gradient angle accurately.

It is understood that the above-described embodiments are intended toillustrate rather than limit the invention. Variations may be made tothe embodiments and methods without departing from the spirit of theinvention. Accordingly, it is appropriate that the appended claims beconstrued broadly and in a manner consistent with the scope of theinvention.

1. A surface topography detector, comprising: a first sensor with afirst central axis; a second sensor with a second central axis, thefirst sensor and the second sensor being arranged in a manner such thatan angle equal to or less than 90 degrees is defined between the firstcenter axis and the second center axis; and a digital control unitelectrically connected with the first sensor and the second sensor, thedigital control unit being configured for processing output signals fromthe first sensor and the second sensor and controlling movement of thefirst sensor and the second sensor.
 2. The surface topography detectoras claimed in claim 1, wherein the first sensor or the second sensor isan optical interference sensor.
 3. The surface topography detector asclaimed in claim 1, wherein the first sensor or the second sensor is aninductive transducer.
 4. The surface topography detector as claimed inclaim 1, wherein the output signals from the first sensor and the secondsensor include information on surface topography of a detected locationon the workpiece and corresponding positions of the first sensor and thesecond sensor.
 5. A method for detecting a surface topography of aworkpiece, comprising the steps of: arranging a first sensor with afirst central axis and a second sensor with a second central axis in amanner such that an angle is defined between the first center axis andthe second center axis, the angle being equal to or less than 90degrees; determining detecting locations of the first sensor and thesecond sensor; detecting the locations on the surface using the firstsensor and the second sensor; and processing output signals from thefirst sensor and the second sensor thereby obtaining a detecting result.6. The method as claimed in claim 5, wherein the first or second sensoris an optical interference sensor.
 7. The method as claimed in claim 5,wherein the first or second sensor is an inductive transducer.
 8. Themethod as claimed in claim 5, wherein the output signals of the firstsensor and the second sensor include information of surface topographyof the workpiece and positions of the first sensor and the secondsensor.